$Cu^{2+}$ ions will be reduced to $Cu^{+}$ ions by the addition of an aqueous solution of

For the four successive transition elements $(Cr, Mn, Fe, \text{ and } Co)$,the stability of $+2$ oxidation state will be in which of the following order?
(Atomic numbers: $Cr = 24, Mn = 25, Fe = 26, Co = 27$)

Explain the trends in $E_{M^{3+}/M^{2+}}^{o}$ electrode potential.

$E^{\circ}_{M^{3+} \mid M^{2+}} \text{ (in } V\text{) is highest for}$

The number of ions from the following that have the ability to liberate hydrogen from a dilute acid is. . . . . . . .$Ti^{2+}, Cr^{2+}, V^{2+}$

Which of the following metal oxides is not amphoteric?